Provisional Patent Application No. 60/152,826, filed 7 September 1999, U. S.

Provisional Patent Application No. 60/166,240, filed 18 November 1999, and U. S. Patent Application No. 09/-,-, (unknown), filed 31 August, 2000.

STATEMENT RE FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT Not Applicable REFERENCE TO A"MICROFICHE APPENDIX" Not Applicable BACKGROUND OF THE INVENTION Field of the Invention The present invention relates generally to apparatus and method for controlling output apparatus in response to actuation of a sensor by a human body member. More particularly, the present invention pertains to control of a controllable device by human-head actuation of a tilt-axis X-Y input device, conditioning of the resultant X and Y signals, and human interaction, such as voice interaction, with the conditioned X and Y signals, whereby various types of apparatus, such as power wheelchairs or computers, may be controlled.

Description of the Related Art Human dexterity, as well as human ingenuity, has been responsible for much of the increase in productivity during the years of the industrial revolution. The marvels of cooperation between the human brain and the human hand include translation of text into type, or computer files, by accurate and rapid manipulation of a keyboard.

In addition, human dexterity has allowed the foot to cooperate in many complex tasks. For instance, for decades, the foot has been used to control functions needed in transcribing dictated text.

For those with good manual dexterity, supplementing hand manipulation with manipulation by another body member has increased productivity. But for persons who, because of paralysis or some other physical limitation, do not have use of their hands, substituting the use of one body member for an unusable body member can make the difference between self- reliant productivity and dependence.

Thus, two groups can be helped by body-member actuation of input devices. Those with good manual dexterity can become more productive, and those who have severe physical limitations can become more productive and self-reliant.

With regard to the physically handicapped, electrically-propelled wheelchairs have opened the way for independent living and increased productivity for many.

For control of electrically-propelled wheelchairs, commonly two separate input devices are included in an X-Y input device that receives mechanical inputs with respect to X and Y axes, and that produce two separate electrical outputs with respect to X and Y axes and a mechanical input.

X-Y input devices of the joystick type are commonly used to control not only speed but also steering of electrically-propelled wheelchairs. That is, an electric motor is drivingly connected to each one of left and right wheels, so that steering and pivotal turns are controlled by selectively controlling speeds and directions of rotation of the electric motors.

X-Y input devices for power wheelchairs have been of two distinct types. The interface of the present invention, as taught herein, may be used with either type.

In a first type, one transducer has been oriented for actuation with respect to a Y axis, and another transducer has been oriented for actuation with respect to an X axis.

In this first type of X-Y input device, inputs with respect to the Y axis are used to control forward and reverse directions of propulsion and their speeds. The X axis inputs are used to provide differential speeds of the motors, and counter-rotational motor speeds, if desired, thereby controlling turns and optionally producing pivotal turns.

In a second type, typically, the transducers are rotated approximately forty-five degrees from alignment with a Y axis; so that movement of a joystick along the Y axis actuates both transducers, and movement of the joystick along the X axis also actuates both transducers.

Direction of rotation of both motors, difference in rotation speed of the motors, and therefore speed, turns, and pivotal turns are controlled by selectively positioning the joystick with respect to the X and Y axes.

While electrically-propelled wheelchairs and joystick X-Y input devices have freed tens of thousands from needing help in moving from one place to another, other thousands, paralyzed from the neck down, have eagerly looked forward to the day when they would have this same freedom.

In addition to those who are paralyzed from the neck down, many others are able to control a power wheelchair by movement of some other body member, such as a hand or a foot, but only if the control signals that they produce can be sufficiently conditioned to meet their individual needs and manual dexterity skills. The conditioning circuitry of the present invention fulfills this need.

There has been an earnest attempt to help paralyzed persons control a power wheelchair by blowing and/or sucking on a tubular mouthpiece. The results have not been satisfactory, especially for those who cannot breath without a ventilator.

However, in Lautzenhiser U. S. Patent No. 5,635,807, issued 3 June 1997; and in Lautzenhiser Continuation-in-part Application No. 08/864,466, filed 28 May 1997, abandoned, and refiled on 10 March 2000 as Provisional Patent Application No. 60/188,431; Lautzenhiser teaches a tilt-axis X-Y sensor and interface circuitry for control of a power wheelchair by tilting one's head or some other body member.

The state of the art has further been advanced by Lautzenhiser in Lautzenhiser U. S. Patent Application No. 09/090,368, filed 4 June 1998; in Lautzenhiser PCT Patent Application No. PCT/US98/11579, filed 5 June 1998; in Lautzenhiser Provisional Patent Application No. 60/147,055, filed 3 August 1999; in Lautzenhiser Provisional Patent Application No. 60/162,087, filed 28 October 1999; and in Lautzenhiser Continuation-in-part Application No.

09/483,705, filed 14 January 2000; in which tilt-axis X-Y sensors are taught that use light-sensitive transducers.

For control of a controllable device, such as a power wheelchair, by a tilt-axis X-Y sensor, means must be provided for interfacing the two. Further, for optimum control, by a human head or an other human body-member, or inclinations of a tilt-axis X-Y input device, provision must be made for conditioning control signals that are produced by tilting the X-Y input device, thereby tailoring the system to the user's motor skills.

Ideally, as taught in the present patent application, provisions for signal conditioning should include: selectively-adjustable proportioning of the output of the tilt-axis X-Y input device, unless selectively-adjustable sensitivity is provided by the tilt-axis X-Y input device; tremor control to dampen signals produced with body-movement tremors; signal limiting to limit maximum speeds; a null-width generator, together with a null-width adjuster, to enhance controllability; overrange shutdown to avoid an accident if the user loses consciousness, has involuntary muscle spasms, or if the tilt-axis X-Y input device is knocked off of the head; and adjustable turn sensitivity to automatically slow the forward speed as a function of turn signals.

As taught by Lautzenhiser in U. S. Patent No. 5,635,807 and in Lautzenhiser Provisional Patent Application No. 60/188,431, it is important to provide both soft starts and soft stops for power wheelchairs. Even if an emergency stop is demanded, it must not be made with an abruptness that will catapult the occupant out of the wheelchair, nor should a start be with such abruptness as to be disconcerting.

If a tilt-axis X-Y input device is used, automatic nulling of the output signal would be highly desirable. Inexact positioning of the tilt-axis X-Y input device on the head, or other body member, of a user, and/or inexact positioning of the head, or other body member, of the user will cause a power wheelchair to start in an unpredictable direction at an unpredictable speed. In addition, inexact positioning of the tilt-axis X-Y input device on the head, or other body member, of the user will result in the head, or other body member, of the user needing to be positioned in an uncomfortable position to hold the wheelchair in a no-speed condition.

However, if automatic nulling were provided for the wheelchair, or other controllable device, there would be no movement of the wheelchair until the tilt-axis X-Y input device were moved from the automatically-nulled position, and the wheelchair could be held in a no-speed position with his head in a comfortable position.

If automatic nulling is to be accomplished, means must be provided for holding the output of the interface to precise null during a time delay while automatic nulling is accomplished. And the automatic nulling device must remain drift free for a number of hours.

With regard to tremor control, this kind of signal conditioning is taught in Lautzenhiser U. S. Patent No. 4,906,906, issued 6 March 1990; in Lautzenhiser U. S. Patent No. 4,978,899, issued 18 December 1990; and in Lautzenhiser U. S. Patent No. 5,012,165, issued 30 April 1991, now abandoned.

In U. S. Patent No. 5,635,807, issued 3 June 1997; and also in Provisional Patent Application No. 60/188,431, filed 10 March 2000; Lautzenhiser teaches head control of a tilt-axis X-Y input device, control by tilting some other body member, selective proportioning of output signals, signal limiting to adjustably limit maximum speeds, overrange shutdown, and ajustable turn signal conditioning.

In U. S. Patent Application No. 09/090,368, filed 4 June 1998; in PCT Patent Application No. PCT/US98/11579, filed 5 June 1998; in Provisional Patent Application No. 60/147,055, filed 3 August 1999; in Provisional Patent Application No. 60/162,087, filed 28 October 1999; and in Continuation-in- part Application No. 09/483,705, filed 14 January 2000; Lautzenhiser teaches, not only X-Y input devices that use light-sensitive transducers, but also selectively controlling the sensitivity of X-Y input devices.

All of the aforesaid Lautzenhiser U. S. Patents, non-provisional patent applications, and provisional patent applications are incorporated herein by reference thereto.

Considering now those who have good motor skills, touch typing depends upon having the hands located in standard positions on a keyboard so that any key may be struck without the necessity of looking at the keyboard.

Typically, when using modern computer programs, a computer mouse is moved over a desk surface, and a computer cursor moves proportional to movement of the mouse. Using the mouse, the cursor is moved to"point"to an icon or words on the monitor representing a desired computer program or to a computer function. Then the user"clicks"on the program or function by pressing a button on the mouse, thereby activating the selected program or function.

The invention and popular use of"point and click"programs have been both a help and a nuisance to computer users."Point and click"programs have relieved computer users of the necessity of remembering and using complex commands to actuate programs and program operating procedures. But they have degraded the typing skill of good typists because of the need to move a hand from the keyboard to a mouse.

Thus, the mouse of the present invention, that can be worn on the human head, much as a telephone headset is worn, or as an integral part of a telephone headset, allows a touch typist to keep both hands on standard positions on the keyboard while pointing with the head-attached mouse.

Whether it be a commercial user who takes orders on the telephone, an industrial user who does computer-assisted drawing, or a home owner who desires greater productivity, the head-attached mouse of the present invention provides increased productivity.

With regard to the physically handicapped, use of the head-actuated mouse of the present invention, together with an addition human interface provided by the present invention, allows use of complex computer programs, such as computer-assisted drawing programs, even by those who are paralyzed from the neck down.

In a first aspect of the present invention, a method for controlling a computer comprises: body-member actuating a tilt-axis X-Y input device to a tilt angle wherein an output signal is produced; and moving a cursor on a monitor of the computer in response to the output signal.

In a second aspect of the present invention, a method for controlling a controllable device comprises: body-member actuating an input device to an approximate null position; developing an error signal that is a function of the

difference between the initializing output signal of the input device and the null; preventing the initializing output signal from actuating the controllable device; and correcting subsequent output signals for the initializing output signal.

In a third aspect of the present invention, a method for controlling a controllable device comprises: body-member actuating an input device to a first position wherein an output signal is within a null width, and to a second position wherein the output signal is outside the null width; preventing the output signal from actuating the controllable device when the output signal is within a null width; and progressively allowing the output signal to actuate the controllable device when the output signal changes from being within its null width to being outside of its null width.

In a fourth aspect of the present invention, a method for controlling X and Y actuation of a controllable device in response to respective ones of X and Y output signals comprises: preventing either the output signals from actuating the controllable device when both of the X and Y output signals are within respective null widths; releasing the X actuation from the preventing step at a first rate when the X output signal changes from being within its null width to being outside of its null width; and releasing the Y actuation from the preventing step at a different rate when the Y output signal changes from being within its null width to being outside of its null width.

In a fifth aspect of the present invention, a method for controlling a controllable device with spaced-apart left and right wheels comprises: controlling forward and reverse speeds of the left and right wheels as a function of a Y output signal; controlling differences in speeds of the left and right wheels as a function of an X output signal; and reducing the forward speed as a function of the X output signal.

In a sixth aspect of the present invention, a method for controlling a controllable device comprises: tilting a body-member to a tilt angle; non- optically producing an output signal as a function of the tilt angle; and actuating the controllable device in response to the output signal.

BRIEF SUMMARY OF THE INVENTION An interface is provided for use between an X-Y input device, which preferably is a tilt-axis X-Y sensor, but which may be any other type of X-Y input device, including a joystick X-Y input device, and a controllable device which may be a power wheelchair, a computer, or an other type of controllable device.

The tilt-axis X-Y sensor is secured to a user's head, or fastened to one or two other body members, in a position in which, with the body member (s) comfortably positioned, the tilt-axis X-Y sensor will provide an output voltage that approximates a null voltage.

With the head, or other body member (s), held in this approximate-null position, the interface automatically nulls the output voltage during an ajustable time delay, so that, at start up, there will be no activity by the controllable device until a tilt-angle command is given by the user.

Subsequently, when the user actuates the tilt-axis X-Y sensor, the interface automatically compensates the output signals of the tilt-axis X-Y sensor for the approximate null.

The interface includes one of three embodiments of a null-width generator. Any one of the null-width generators allows for selective adjustment of null widths in accordance with individual motor skills of users, so that the head of the user may be moved within selectable forward/reverse and left/right tilt angles before an actuating signal is sent to the controllable device.

Optionally, included in two of the ajustable null-width generators are rate-of-change controllers, one each for X and Y axis signal voltages. The rate- of-change controllers feed the null-width voltages back into the system, at controlled rates, the voltages that were taken from the X and Y control voltages by the null-width generator.

The rate-of-change controllers are especially valable for preventing steering instability of power wheelchairs that is called"fish tailing."Typically, to enhance steering stability, the RC value of the rate-of-change controller for the X axis, that controls turns, is made about one-fourth of the RC value for the rate-of-change controller for the Y axis.

If the tilt-axis X-Y sensor is considered to be a first human input device, then the present invention optionally uses a second human input device. This second human input device may be a voice-recognition interface device, a sound-wave input device, or any other human input device that can be used to control a function of the system.

For instance, if the present invention is used for"point and click" control of computer functions, and if a tilt-axis X-Y sensor is used for"pointing," the second human input device may provide only the"clicking"function. Or the second human input device may translate voice commands into complex computer operations.

This second human input device, which may be a voice-recognition IC, is connected to the remaining circuitry by means of a human interface device which may be a microprocessor. Optionally, the second input device may input directly into the controllable device.

The interface of the present invention also provides tremor control, signal limiting, signal proportioning, over-range shutdown, and turn signal conditioning. Tremor controlling, automatic null compensating, signal limiting, signal proportioning, null-width generating with both null-width adjusting and rate-of-change compensating, and turn signal conditioning, provide a system that can be adjusted for successful operation by users within a wide range of motor ski ! ! s.

The interface may be connected directly to a power control unit or a controllable device, or a microprocessor may be interposed between the interface and the controllable device. Either way, indicator lights are provided to inform the user of the status of the interface.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS FIGURE 1 is a block diagram of the interface, showing components for one axis in labeled boxes, showing components for the other axis in boxes that are numbered but not labeled, and interposing labeled boxes for components that function with both axes, but omitting turn signal conditioning components; FIGURE 2A is a symbolic drawing of a joystick X-Y input device in which respective ones of the input devices are aligned with X and Y axes, so

that one tilt sensor controls forward and reverse speeds, and the other controls turns; FIGURE 2B is a symbolic drawing of a joystick X-Y input device in which the transducer axes are about forty-five degrees from the X and Y axes, so that both transducers control speeds and turns; FIGURE 3A is a symbolic drawing of a tilt-axis X-Y sensor in which the tilt axes of the transducers are parallel to X and Y axes, so that one tilt transducer controls speeds and the other controls turns; FIGURE 3B is a symbolic drawing of a tilt-axis X-Y sensor in which tilt axes of the transducers are at about forty-five degrees from the X and Y axes, so that both tilt transducers control speeds and turns; FIGURE 4 is a simplifie top view of a prior art wheelchair, showing primarily parts associated with the subject invention; FIGURE 5 is a side elevation of a head of a person wearing a tilt-axis X-Y sensor that may be used in combination with the interface of the present invention; FIGURE 6 is a rear elevation of the head of the person of FIGURE 6, taken substantially as shown by view line 6-6 of FIGURE 5; FIGURE 7A is a graph of a signal voltage, as produced by a tilt sensor, in which the resultant null voltage is offset to an approximate null by approximate positioning of the user's head, and the signal voltage includes fluctuations caused by body tremors of the user; FIGURE 7B is a graph of the signal voltage of FIGURE 7A, but with voltage fluctuations removed by the tremor conditioner; FIGURE 7C is a graph of the signal voltage of FIGURE 7B, but with the approximate null corrected to a precise null; FIGURE 7D is a graph of the signal voltage of FIGURE 7B, showing shutdown limits, both plus and minus; FIGURE 7E is a graph of the signal voltage of FIGURE 7C, but with control signal limiting; FIGURE 7F is a graph of the signal voltage of FIGURE 7E, but with signal proportioning;

FIGURE 7G is a graph of the signal voltage of FIGURE 7F, but with adjustable null width; FIGURE 8 is a schematic and a block diagram of a portion of the interface of FIGURE 1, showing components used for one axis of the interface of FIGURE 1, except for omitting a selected one of three different null-width generators, and except for omitting a selected one of three different turn signal conditioners; FIGURE 8A is a null-voltage generator for use with the interface of FIGURES 1 and 8; FIGURE 9 is a first of three embodiments of null-width generators for use with the interface of FIGURES 1 and 8; FIGURE 10 is a preferred embodiment of a null-width generator for use with the interface of FIGURES 1 and 8; FIGURE 11 is a variation of the null-width generator of FIGURE 10 in which the mechanical relay of FIGURE 10 is replace by a solid-state bilateral switch; FIGURE 12 is a prior-art schematic of a turn signal conditioner that is usable as a part of the interface of FIGURE 1 when the transducers are of the type shown in FIGURES 2B and 3B; FIGURE 13 is a schematic drawing of a turn signal conditioner that is usable as a part of the interface of FIGURE 1 when the transducers are of the type shown in FIGURES 2A and 3A; FIGURE 14 is a schematic drawing of a turn signal conditioner that is usable as a part of the interface of FIGURE 1 when the transducers are of the type shown in FIGURES 2A and 3A, and that conditions both forward and reverse signals as a function of turn signals; FIGURE 15 is a schematic drawing of an X-Y null indicator that produces a light of reduced intensity when both X and Y axes are nulled; FIGURE 16 is a schematic drawing of a second embodiment of an X-Y null indicator that produces a light of reduced intensity when both X and Y axes are nulled;

FIGURE 17 is a side elevation, taken substantially the same as FIGURE 5, showing a tilt-axis X-Y sensor mounted onto a user's head, and showing a chin-strap switch that enables hand-free"clicking"of mouse functions; and FIGURE 18 is a block diagram of an embodiment of the present invention in which apparatus for control of a controllable device, such as a computer, includes a first human-input device which preferably is a tilt-axis X-Y sensor, a second human input device which preferably is a voice-recognition chip, and a human interface device, which preferably is a microprocessor.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIGURE 1, a signal conditioner, or interface, 10 optionally includes all of the portions shown in FIGURE 1, except tilt transducers, input devices, or tilt sensors, 12A and 12B which are a part of a tilt-axis X-Y input device, or first human input device, 14, which are shown in phantom lines, and which may include tilt transducers of any suitable type, or which may be mechanically or manually-actuated transducers of any suitable type. Although not shown in FIGURE 1, the signal conditioner 10 includes one of the turn signal conditioners of FIGURES 12,13, or 14.

Referring to FIGURES 2A, 2B, 3A, and 3B, a joystick X-Y input device, or first human input device, 16 of FIGURE 2A includes input devices, transducers, or rotary-shaft potentiometers, 18A and 18B that are oriented along X and Y axes, respectively. Pivotal movement of a joystick 20 around the X axis actuates the potentiometer 18A, and pivotal movement of the joystick 20 around the Y axis actuates the potentiometer 18B.

In FIGURE 2B, potentiometers 18A and 18B of a joystick X-Y input device, or first human input device, 22 are disposed along axes 24A and 24B and are oriented at approximately forty-five degrees to the X and Y axes.

Movement of the joystick 20 around the X axis actuates both potentiometers, 18A and 18B, and actuation of the joystick 20 around the Y axis actuates both potentiometers, 18A and 18B.

Referring now to FIGURES 3A and 3B, tilt transducers, or tilt sensors, 26A and 26B, of a tilt-axis X-Y input device, or first human input device, 28, which may be used for the sensors 12A and 12B for the X-Y input device 14 of

FIGURE 1, may be either optical or non-optical. With regard to non-optical sensors, capacitive inclination sensors are especially suitable for use as tilt-axis X-Y input devices in the present invention.

When two separate tilt transducers, 26A and 26B, of the non-optical type are used, Inclinometers, Part No. SCA600 CBBH1, manufactured by VTI Hamlin, Farmington Hills, Michigan, are preferred.

Another preferred non-optical tilt transducer is Inclinometer Part No.

ADXL202, manufactured by Analog Devices, Norwood, Maine which includes both tilt sensors, 26A and 26B, of the tilt-axis X-Y input device 28 in a single unit.

As for optical sensors, the light-sensitive transducers as taught by Lautzenhiser Continuation-in-part Application, S/N 09/483,705, filed 14 January 2000, is an excellent choice for use as the tilt-axis X-Y sensor 14 of FIGURE 1.

In FIGURE 3A, the tilt transducers, or tilt sensors, 26A and 26B, of a tilt-axis X-Y input device, or first human input device, 28, are oriented long tilt axes 30A and 30B that are parallel to the Y and X axes, respectively, so that tilting around the X axis causes the tilt sensor 26B to produce a signal, and tilting around the Y axis causes the tilt sensor 26A to produce a signal.

In contrast to the tilt-axis X-Y input device 28 of FIGURE 3A, in a tilt- axis X-Y input device, or first human input device, 32 of FIGURE 3B, the tilt axes 30A and 30B of the tilt sensors 26A and 26B are oriented at approximately forty-five degrees to the X and Y axes. Thus, the tilt-axis X-Y input device 32 functions similarly to the joystick X-Y input device 22 of FIGURE 2B.

This basic difference in X-Y input devices, as described above, has no effect on the operation of the interface 10, except if turn signal conditioning is needed or desired.

When X-Y input devices are used that are configured as shown in FIGURES 2A and 3A, a signal voltage for controlling forward and reverse propulsion and the speeds of propulsion is produced by the tilt sensor 12A of FIGURE 1, and a signal voltage for controlling turns is produced by the tilt sensor 12B. For this type of X-Y input device, if needed or desired, the turn signal conditioner of either FIGURE 13 or FIGURE 14 may be used.

But when X-Y input devices are used that are configured as shown in FIGURES 2B and 3B, both propulsion and turn voltages are produced by both tilt sensors, 12A and 12B. For this type of X-Y input device, if needed or desired, the prior-art turn signal conditioner of FIGURE 12, or any other turn signal conditioner taught by Lautzenhiser in U. S. Patent 5,635,807, may be used.

Referring again to FIGURE 1, it should be noticed that there are three different groups of boxes, or blocks, in the block diagram.

In a first group, located closest to the bottom of the drawing, the boxes are numbered, but they are not labeled. These unlabeled boxes pertain to control signals produced by the tilt sensor 12B.

A second group of boxes, located closest to the top of the drawing, is the same as the unlabeled boxes, except that labels are inserted into the boxes.

This second group of boxes pertain to control signals produced by the tilt sensor 12A.

A third group of boxes is disposed between the other two groups. This labeled group of boxes pertain to control signals produced by both tilt sensors, 12A and 12B.

Continuing to refer to FIGURE 1, the first and second groups of boxes of the interface 10 include tremor controls, 40A and 40B, buffers, 42A and 42B, offset storage devices, or offset storage capacitors, 44A and 44B, offset buffers, 46A and 46B, signal limiters, 48A and 48B, signal proportioners, 50A and 50B, and null-width generators, 52A and 52B.

The buffers 42A and 42B, the offset storage devices 44A and 44B, and the offset buffers 46A and 46B, cooperate to provide null compensators 53A and 53B, respectively.

The third group of boxes of the interface 10 includes an overrange comparator 54, a shut-down latch 56, an ON/OFF latch 58, a momentary- contact switch 60, a null timer 62, an amber LED standby indicator 64A, a blue LED delay indicator 64B, and a green LED active indicator 64C. A proportionality adjuster 66 is connected to one or both of the signal proportioners, 50A and 50B, and a null-width adjuster 68 is connected to one or both of the null-width generators, 52A and 52B.

The overrange comparator 54 is connected to conductors 70A and 70B.

The shut-down latch 56 is connected to the conductors 72A and 72B, and the null timer 62 is also connected to the conductors 72A and 72B.

Finally, a null voltage N, which preferably is a positive DC voltage, and which usually is approximately one-half of the supply voltage, is developed by a null voltage divider, or null voltage generator, which will be numbered and described subsequently in conjunction with FIGURE 8A. For now, it is important to know that wherever the capital N appears on FIGURE 1, a precise null voltage, that preferably is about one-half of the supply voltage, is supplied.

Referring now to FIGURE 4, while the interface 10 may be used to control various types of controllable devices, assume that it is operatively connected to electric motors 78A and 78B of a power wheelchair, or controllable device, 80 via a power interface, not shown, nor a part of the present invention. The electric motors 78A and 78B are drivingly connected to wheels 82A and 82B.

Referring now to FIGURES 5 and 6, while user actuation of the transducers 12A and 12B may be by any suitable means, such as movement of any body member, as taught by Lautzenhiser in U. S. Patent No. 5,635,807 and in Provisional Patent Application No. 60/188,431, in the discussion that follows it will be assumed that the tilt-axis X-Y input device 14 is mounted onto a head, or body member, 83 of a person 84, by any suitable means.

Further it is assumed that the tilt-axis X-Y input device 14 has been adjusted, both fore and aft and side to side, to be aligned approximately with null angles, or horizontal angles, 85 and 86, of FIGURES 5 and 6, respectively, when the head 83 of the person 84 is in a comfortable position.

Referring again to FIGURE 1, in the following discussion, only voltage signals developed by the tilt sensor 12A, and components that cooperate with voltage signals produced by both tilt transducers, 12A and 12B, will be considered, since this discussion may also be applied to voltage signals developed by the tilt sensor 12B.

Assume that a switch, not shown, which is preferably voice actuated, has been thrown to provide electrical power from a battery, not shown, to the interface 10. At this time, the amber LED standby indicator 64A is lit.

A preferred component for voice actuation of the aforementioned switch is manufactured by Sensory, Inc. of Sunnydale, California. The part name is"Voice Direct,"and the part number is RSC-264T.

Referring now to FIGURES 1,5, and 6, when the person 84 of FIGURES 5 and 6 is ready to move, he activates the momentary-contact switch 60 with his head 83, or activates some other switch, by any suitable means, such as the voice-actuated component listed above, thereby latching the ON/OFF latch 58 of FIGURE 1 to ON, starting the null timer 62, and thereby providing a time delay.

At the start of the time delay, the amber LED standby indicator 64A is turned off, and the blue LED delay indicator 64B is turned on, and the green LED active indicator 64C is turned on.

Because the person 84 has tilted his head 83 sideways to activate the momentary-contact switch 60, at least one of the tilt sensors, 12A or 12B, is producing a signal voltage that is far from the null voltage.

After tilting his head sideways to activate the momentary-contact switch 60, the person 84 then moves his head 83 back to a comfortable position wherein the tilt-axis X-Y input device 14 is approximately aligned with null angles, or horizontal angles, 85 and 86 of FIGURES 5 and 6, respectively.

Subsequently, the person 84 will be able to control speeds and turns of the power wheelchair 80 of FIGURE 4 by tilting his head 83 within head inclination angles, 87A and 87B of FIGURE 5, and within head inclination angles 88A and 88B of FIGURE 6.

However, after moving his head 83 to approximately the null angles, 85 and 86, the tilt-axis X-Y input device 14 of FIGURE 1 produces approximately nulled voltages.

That is, if a ten-volt system is used, and a null voltage N is five volts, then an approximate null position of the tilt-axis X-Y input device will produce a voltage roughly in the range of four to six volts, which is one volt above or below the null voltage, more or less.

During the time delay of the null timer 62, which may be ajustable to times preferably in the range of 0 to 7 seconds, the null timer 62 applies the

null voltage N to the conductor 72A, holding the voltage in the conductor 72A to a precise null voltage.

If the person 84 has Parkinson's disease, or some other tremor-inducing disease, one or both of the tilt sensors, 12A and 12B, most likely will be producing a tremoring voltage, as shown by a tremoring voltage curve 90 of FIGURE 7A, so that a tremoring approximate null voltage 92 may be, on the average, a volt or so higher or lower than the precise null voltage N, and will include voltage fluctuations, as shown in FIGURE 7A.

As the tremoring approximate null voltage from the tilt sensor 12A is applied to the tremor control 40A, tremoring voltages are averaged, so that a tremor-controlled voltage curve 94 of FIGURE 7B is produced, and a tremor- controlled approximate null voltage, or offset voltage, 96 is produced.

The buffer 42A operates as a follower, faithfully reproducing the output of the tilt sensor 12A in the conductor 70A, so the output of the buffer 42A is also represented by FIGURE 7B.

In the meantime, the conductor 72A of FIGURE 1 is being held at the null voltage N, and the offset buffer 46A serves as a follower, holding its output to the null voltage N.

Therefore, the offset storage capacitor 44A is subjected to a nulling voltage. That is, the offset storage capacitor 44A is subjected to a voltage in the conductor 70A that is produced by the tilt sensor 12A and averaged by the tremor control 40A, and that may be either higher or lower than the precise null voltage N. And the offset storage capacitor 44A is subjected to a voltage in the conductor 72A that is held to the precise null voltage N.

Thus, it can be seen that the offset storage capacitor 44A stores a voltage that is the difference between the approximate null voltage 96 of FIGURE 7B, which may vary a volt or so from the null voltage N, and the precise null voltage of the null voltage N.

At the end of the time delay produced by the null timer 62, the null voltage N is removed from the conductor 72A, and the blue LED delay indicator 64B is turned off, but the green LED active indicator 64C stays on.

At this time, although the tilt sensor 12A may be developing a voltage that would normally cause the power wheelchair 80 of FIGURE 5 to lurch

forward, and although the null voltage N has been removed from the conductor 72A, the offset storage capacitor 44A and the offset buffer 46A cooperate to compensate for the approximate null voltage 96 of FIGURE 7B, so that the power wheelchair 80 does not move.

That is, the approximate null voltage 96 of FIGURE 7B is increased or decreased to a corrected null voltage, or null compensated signal, 98 in a signal voltage curve 100 of FIGURE 7C.

Therefore, instead of lurching forward because of an approximate null voltage 92 of FIGURE 7A, or 96 of FIGURE 7B, the power wheelchair 80 of FIGURE 5 does not move until the person 84 of FIGURES 5 and 6 tilts his head 83 to actuate the tilt-axis X-Y input device 14.

From this time on, until the next shutdown, the null compensator 53A, which includes the buffer 42A, the capacitor 44A, and the offset buffer 46A, offsets the output of the tilt sensor 12A, so that signal voltages delivered to the signal limiter 48A are compensated for the approximate null voltage 96, of FIGURE 7B, that was produced during the time delay.

At the end of the time delay produced by the null timer 62, the green LED active indicator 64C continues to be on, but the blue LED delay indicator 64B is turned off. The person 84 of FIGURES 5 and 6 can now control both speed and turns of the power wheelchair 80 by selectively tilting his head 83 toward angles 87A, 87B, 88A, and 88B.

Leaving consideration of the signal voltages produced by the offset buffer 46A of the null compensator 53A, it is time to consider the overrange comparator 54. Referring again to FIGURE 1, the overrange comparator 54 cooperates with the shut-down latch 56 to limit maximum signal voltages 102A and 102B of a signal voltage curve 104, as shown in FIGURE 7D, that can be produced by the tilt sensor 12A without incurring a shutdown of the interface 10 of FIGURE 1 and the power wheelchair 80 of FIGURE 4.

Whenever a signal voltage produced by the tilt sensor 12A of FIGURE 1 goes beyond either of the maximum signal voltages, 102A or 102B, of the signal voltage curve 104, either plus or minus, the overrange comparator 54 and the shut-down latch 56 cooperate to apply the null voltage N to the conductor 72A, thereby initiating a shutdown.

That is, whenever the conductor 72A is brought to the null voltage N, by any means, the offset buffer 46A holds its output to the null voltage N, and the power wheelchair 80 of FIGURE 4 stops.

Prior to overrange shutdown, the green LED active indicator 64C is lit.

Now, to indicate shutdown, preferably the amber LED standby indicator 64A and the green LED active indicator 64C flash alternately. By these flashing lights, if the person 84 is conscious, and is able to control the power wheelchair 80, he knows that he has overranged the tilt-axis X-Y input device 14, and that he must restart the interface 10.

The overrange comparator 54 provides a safety device for an occasion in which the tilt-axis X-Y input device may be knocked from the head 83 of the person 84 of FIGURES 5 and 6. Also, the overrange comparator 54 provides a safety device for any occasion in which the person 84 may drop his head 83, due to sleep, unconsciousness, or some involuntary muscle disorder.

In any of these situations, instead of the power wheelchair 80 of FIGURE 4 moving dangerously out of control, the overrange comparator 54 and the shut-down latch 56 cooperate to apply the null voltage N to the conductor 72A. With the conductor 72A held to the null voltage, the power wheelchair 80 comes to a safe stop.

The person 84, if conscious and both mentally and physically able, after repositioning his head 83 to approximate null angles 85 and 86 of FIGURES 5 and 6, respectively, may restart the interface 10 by actuating the switch 60 with his head 83, thereby toggling the ON/OFF latch 58 to OFF.

With the ON/OFF latch 58 toggled to OFF, the shut-down latch 56 is released, and the interface 10 is ready to restart.

As shown in FIGURE 1, preferably, the overrange comparator 54 is connected to the conductor 70A wherein the approximate null voltage 96 of FIGURE 7B exists. However, the overrange comparator 54 may be connected to the conductor 72A, so that the overrange comparator 54 is actuated by a corrected null voltage 98 of FIGURE 7C.

Returning now to consideration of signal voltages exiting from the offset buffer 46A, and referring now to FIGURE 7E, control voltages delivered to the

signal limiter 48A from the offset buffer 46A are limited to voltage magnitudes, 106A and 106B of a signal voltage curve 108 of FIGURE 7E.

The limited voltage magnitudes, 106A and 106B, are limited to magnitudes that are reasonable for the most skilled person 84 of FIGURES 5 and 6, and his ability in positioning his head 83 to achieve the desired control of speeds and turns of the power wheelchair 80 of FIGURE 4. More particularly, the signal limiter 48A limits maximum speeds of the power wheelchair 80 to a safe value for the most skilled person 84.

It should be noticed that, since the overrange comparator 54 is upstream of the signal limiter 48A, the signal limiter 48A can function to limit maximum signal voltages without interfering with the overrange comparator 54.

Next, control voltages delivered to the signal proportioner 50A are adjustably proportioned in accordance with the skill of a particular person 84 of FIGURES 5 and 6 by selectively adjusting the proportionality adjuster 66, thereby producing a proportioned voltage curve 110 of FIGURE 7F.

Proportioned signal voltages are then delivered to the null-width generator, 52A or 52B, of FIGURE 1 wherein null widths 112A and 112B of FIGURE 7G are selectively adjusted by adjustment of the null-width adjuster 68.

Although not illustrated in FIGURE 7G, since the null-width generator, 52A disregards signals up to the selected null level, a maximum magnitude 114 of a signal voltage curve 116 is decreased by the voltage magnitude of the selected null level that is associated with the null width 112A.

With regard to FIGURES 8-16, for the readers convenience, manufacturer's pin numbers are included on the drawings, whether or not these pin numbers are used in the detailed description. In addition, connections to transistors and MOSFETS are labeled for the convenience of the reader, whether or not they are used in the detailed description.

Referring now to FIGURES 1 and 8, FIGURE 8 includes some of the labeled boxes of the interface 10 of FIGURE 1, but omits all unlabeled boxes.

That is, FIGURE 8 includes portions that pertain to the tilt sensor 12A, and includes labeled boxes that cooperate with control signals produced by both transducers, 12A and 12B, but omits portions of the interface 10 that pertain to the ti It sensor 12 B.

Since the present invention includes three different null-width generators, FIGURES 9,10, and 11, any pair of which may be used as a part of the interface 10 of FIGURE 8, FIGURE 8 does not include a null-width generator. Further, the present invention includes three different turn signal conditioners, FIGURES 12-14, any one of which can be used with the interface 10, but none are included in FIGURE 8.

Referring now to FIGURE 8, this drawing includes schematic drawings of selected ones of the labeled and numbered blocks of FIGURE 1 that are numbered the same as the labeled blocks of FIGURE 1. In addition, other labeled and numbered blocks of FIGURE 1 are reproduced in FIGURE 8, so that the reader may more easily understand the various functions and relationships, although not all of these labeled blocks are included in the following description.

The tremor control 40A, which receives a signal voltage from the tilt sensor 12A, includes a resistor R1 and capacitors, C1 and C2. The resistor R1 and the capacitors C1 and C2 cooperate to form a RC circuit that provides tremor control, as previously discussed in conjunction with FIGURES 1,7A, and 7B.

The buffer 42A receives the conditioned voltage signal from the tremor control 40A at pin 10. The buffer 42A is a high input-impedance operational amplifier U1C that is connected as shown to provide a high-isolation follower, so that the smoothed voltages produced by the tremor control 40A are reproduced in pin 8.

The offset storage device 44A receives the offset voltage 96 of FIGURE 7B from the tremor control 40A through the conductor 70A. The offset storage device 44A is a capacitor C3 of the type that will hold its charge for extended periods of time by virtue of using polyester insulation.

The offset buffer 46A is a high input-impedance operational amplifier, U1 D. Pin 12 of the operational amplifier U1 D is connected to the capacitor C3 by the conductor 72B, and the operational amplifier U1 D is connected as shown to provide a high-isolation follower.

The null timer 62 holds the conductor 72A at the null voltage N. Thus, the approximate null voltage 96 in the conductor 70A, as shown by the curve

94 of FIGURE 7B, and the null voltage N, cooperate to apply a charging voltage across the capacitor C3, which is the difference between the approximate null voltage 96, and a precise null voltage, which is the null voltage N.

At the end of the time delay provided by the null timer 62, the null voltage N is removed from the conductor 72A. Thereafter, changes in a control signal voltage produced by the tilt sensor 12A are reproduced in pin 14 of the operational amplifier U1 D by the offset buffer 46A, except that the control signal voltages are corrected to compensate for the approximate null that is produced by inexact mounting of the tilt-axis X-Y input device 14 on the head 83 of a person 84 of FIGURES 5 and 6, and/or inexact positioning of the head 83 during the time delay.

Successful operation of the null compensator 53A, which includes the buffer 42A, the capacitor 44A, and the offset buffer 46A, depends upon holding a precise charge in the capacitor 44A for hours at a time. In the present invention, this has been achieved by three factors.

The capacitor 44A is of the polyester type that has extremely low internal leakage, and that has an extremely slow self-discharge rate. Secondly, the buffers 42A and 46A are FET technology operational amplifiers and have extremely high impedances. They operate in accordance with voltage levels, rather than currents, so they do not place a current drain on the capacitor 44A.

Thirdly, any relays that would discharge the capacitor C3 are of a high-isolation type.

The corrected null-voltage signal, or null-compensated signal 98, is delivered to the signal limiter 48A by a resistor R2 and a conductor 120A. The signal limiter includes npn transistors Q1 and Q2 and diodes CR1 and CR2 that are connected between the source voltage and ground, as shown. The base B of each transistor, Q1 or Q2, is connected to the null voltage.

When the signal voltage in the conductor 120A is greater than the null voltage by approximately 2.5 volts, the transistor Q2 will conduct pulling the signal voltage downwardly toward null, causing a voltage drop across the resistor R2. Conversely, when the signal voltage in the conductor 120A is less

than the null voltage by approximately 2.5 volts, the transistor Q1 will conduct pulling the signal voltage upwardly.

As will be apparent to those skilled in the art, upper and lower limits of the signal limiter 48A depend upon the type of transistors that are used, and both the type and the number of diodes that are used, if any. That is, for a closer range between upper and lower limits, the diodes, CR1 and CR2, may be omitted, and for a higher range, more diodes may be inserted.

Continuing to refer to FIGURE 8, the signal proportioner 50A includes a potentiometer RV1 that is connected in series with the pin 14 of the operational amplifier U1 D, the resistor R2, a resistor R3, a resistor R4, and the null voltage N. Thus, the control signal in the conductor 120A, that is provided by the operational amplifier U1 D and the resistor R2, whether it is a forward signal that is above the null voltage N, or a reverse signal that is below the null voltage N, is selectively proportioned by the potentiometer RV1 in a conductor 122A.

Thus, the potentiometer RV1 is a part of the proportionality adjuster 66 of FIGURE 1, and an other potentiometer, not shown, that is included in the signal proportioner 50B of FIGURE 1, is the other part of the proportionality adjuster 66. When X-Y input devices of the type shown in FIGURES 2B and 3B are used, preferably, the potentiometer, RV1 and an other potentiometer, not shown, are ganged.

Before leaving FIGURE 8, it is important to notice that the conductor 120A carries the limited signal voltage, and that a conductor 122A carries a signal voltage that is both limited and proportioned. All of the null-width generators, FIGURES 12,13, and 14, use the signal voltage in the conductor 122A. The null-width generators of FIGURES 13 and 14 also use the limited signal voltage in the conductor 120A.

Referring now to FIGURE 8A, a null voltage generator, or null voltage divider, 124 includes resistors R5 and R6 that preferably, but not necessarily, have approximately equal resistances. By connecting the resistors R5 and R6 in series between the source voltage and ground, the null voltage N, of FIGURES 1 and 8, is generated.

Referring now to FIGURE 9, a first embodiment of a null-width generator, which is numbered 52A on FIGURES 1 and 9, includes: operational amplifiers, U2A, U2B, and U2D, a capacitor C4, a resister R6, and a potentiometer RV2.

The operational amplifiers U2A and U2D serve as buffers, or followers, and the operational amplifier U2A receives the limited signal voltage at pin 3 from the conductor 122A of FIGURE 8. The operational amplifier U2B is provided with the null voltage N on pin 5, so that, a null width, that may vary from 0.1 up to 0.7 volts on each side of the null voltage, as determined by adjustment of the potentiometer RV2, is subtracted from the limited signal voltage of the conductor 122A, and the remainder is delivered to the operational amplifier U2D. The operational amplifier U2D delivers this same signal voltage to pin 14 and a conductor 126A. Preferably, the potentiometer RV2 has a resistance of 100K ohms.

While the null-width generator 52A provides a valuable function for the interface 10, this particular embodiment has the disadvantage of reducing both maximum and minimum signal voltages, thereby reducing both maximum forward and maximum reverse speeds of a controllable device, such as the power wheelchair 80 of FIGURE 4, because the null width is subtracted from the maximum limited signal voltage and added to the minimum limited signal voltage.

Referring now to FIGURE 10, a null-width generator 130A is provided that not only obviates the aforementioned disadvantage of the null-width generator 52A, but that also includes a significant advantage that will be described subsequently.

The null-width generator 130A includes comparators U3A and U3B; an operational amplifier U1A that serves as a buffer or follower, that has a high input-impedance, and that is configured as a follower; a n-channel MOSFET Q3; a normally-open mechanical relay 132A having a relay coil 134A and a pair of normally-open contacts 136A; resistors R7, R8, R9, R10, R11, and R12, a potentiometer RV3, and capacitors C5, C6, and C7.

The resistors R8, R9, and R10, and the potentiometer RV3 cooperate to provide ajustable high and low limits on pins 5 and 6 of the comparators U3A

and U3B. The signal voltage that has been limited by the signal limiter 48A in the conductor 120A, is applied to pins 4 and 7, and the resistor R11 serves as a pull-up resistor for the outputs at pins 1 and 2.

The capacitors C6 and C7 cooperate with the resistor R12 to provide a RC circuit 138A. As shown, the capacitors C6 and C7 are positioned back-to- back to provide a non-polarized capacitor. Optionally, a single, non-polarized capacitor may be used.

It should be noticed that it is the limited signal voltage of the conductor 120A, and not the proportioned signal voltage of the conductor 122A, that is applied to the comparator U3A.

By selective adjustment of the potentiometer RV3, upper and lower voltage limits may be set that are in the order of 0.1 to 0.7 volts above and below the null voltage N.

When the limited signal voltage in the conductor 120A is either above or below a respective one of the voltage limits, one of the comparators, U3A or U3B, will output a ground. Since the comparators, are of the open collector type, whenever one of the comparators, U3A or U3B, outputs a ground, its ground will pull down the high gate voltage that has been provided by the resistor R11.

However, when the signal voltage in the conductor 120A is within the upper and lower voltage limits, the outputs of both comparators, U3A and U3B, are high at pins 1 and 2, the pull-up resistor R11 applies a high gate voltage to the MOSFET Q3, and the MOSFET Q3, which is an n-channel FET, conducts, thereby energizing the relay coil 134A, thereby closing normally-open contacts 136A, and thereby forcing a voltage in a conductor 140A to increase or decrease to the null voltage N.

Further, the signal voltage in the conductor 140A will be reproduced in a conductor 142A, since the operational amplifier U1A is configured as a fol lower.

Continuing to refer to FIGURE 10 with the contacts 136A of the relay 132A closed and the conductor 140A at the null voltage N, a voltage differential exists across the resistor R12. That is, the proportioned signal voltage in the conductor 122A will be either higher or lower than the null

voltage N in the conductor 140A, and that the capacitors C6 and C7 charge in response to this voltage differential.

While the contacts 136A are closed, the capacitors, C6 and C7, will hold the voltage differential that exists between the conductors 122A and 140A.

However, as soon as actuation of the input device 12A of FIGURE 8 provides a signal voltage, as proportioned by the signal proportioner 50A, that is outside one of the limits, upper or lower, of one of the comparators, U3A or U3B, the gate G of the MOSFET Q3 goes low, the relay 132A is unlatched, and the null voltage N is isolated from the conductor 140A.

Since the operational amplifier U1A is voltage, rather than current operated, there is no current flow from the capacitors C6 and C7 to pin 5 of the operational amplifier U1A. Instead, the capacitors C6 and C7 are discharged by the resistor R12, that is at a rate determined by the voltage differential, the capacitance of the capacitors, C6 and C7, and the resistance of the resistor R12.

If the RC circuit 138A were not included, the voltage differential between the limited signal voltage, in the conductor 122A, and the null voltage N, in the conductor 140A, would be increased by the null voltage almost instantaneously, and the power wheelchair 80, or other controllable device, would start abruptly.

But, with the RC circuit 138A included, discharge of the capacitors C6 and C7, and insertion of the null signal into conductor 140A is at a controlled rate of change.

It becomes evident that the capacitors, C6 and C7, the resistor R12, and the operational amplifier, U1A cooperate to provide a rate-of-change controller 144A that may be included as a part of the null-width generator 130A.

While only the null-width generator 130A, together with its rate-of- change controller 144A, has been described, it should be understood that, if the input device 12A of FIGURE 8 is used to provide a Y, or speed signal input, and if the input device 12B is used to provide an X, or turn signal input, an other null-width generator, not shown, similar to the null-width generator 130A, and its rate-of-change controller, not shown, similar to 144A, would be used.

Further, for some applications it is critical that the rate of change for the X, or right/left turn signal must be lower than the rate of change for the Y, or forward/reverse, signal to prevent fish tailing of the controllable device, such as the power wheelchair 80 of FIGURE 4. For the forward/reverse signal, preferably the capacitors C6 and C7 are 3.3 pfd, and the resistor R12 is 249K ohms, but for the turn signal, the resistor R12 is changed to 1.5 megohms.

Referring now to FIGURE 11, a null-width generator 150A includes components and conductors that are named and like numbered with those for the null-width generator 130A of FIGURE 10, except as follows.

A gate G of a bilateral switch Q4 is connected to pins 1 and 2 of the comparators, U3B and U3A and to the resistor R11, that serves as a pull-up resistor. When the gate G is high, the switch closes, connecting the null voltage N with the signal voltage in the conductor 140A. Operation is as described for the null-width generator 130A of FIGURE 10.

Referring now to FIGURE 12, a turn signal conditioner 156 is one of several turn signal conditioners that are taught by Lautzenhiser in U. S. Patent 5,635,807 for use with input devices of the type shown in FIGURES 2B and 3B.

The turn signal conditioner 156 is connected to two null-width generators, such as the null-width generators 52A and 52B. Alternately, the turn signal conditioner 156 is connected to the null-width generator 130A, and a similar null-width generator, not shown, for the turn signal. Or the turn signal conditioner 156 is connected to the null-width generator 150A, and a similar null-width generator, not shown.

Referring now to FIGURE 13, a turn signal conditioner 160 is one of two that are taught herein for use with input devices of the type shown in FIGURES 2A and 3A.

The turn signal conditioner 160 is connected to two null-width generators, in like manner as described for the turn signal conditioner 156 of FIGURE 12. That is, the turn signal conditioner 160 is connected to either the conductor 126A of FIGURE 9, the conductor 142A of FIGURE 10, or the conductor 142A of FIGURE 11, and to a similar conductor of a null-width generator, such as the null-width generator 52B for the R/L (right/left) turn signal of the input device 12B by a conductor 162.

The turn signal conditioner 160 includes paralleled resistors for the purpose of achieving precise resistances. Since each pair functions as a single resister, each paralleled pair will be named and numbered as if a single resistor were used.

The turn signal conditioner 160 includes operational amplifiers, U4A and U4B, resistors R13-R24, and diodes CR3, CR4, and CR5. The resistors R13 and R14 are input resistors, and the resistors R15 and R16 are feedback resistors, and the remaining resistors, except for the resistor R23, are used to set, or divide, voltages.

As shown in FIGURE 13, the operational amplifier U4A is configured as an inverting amplifier, the operational amplifier U4B is configured as a non- inverting amplifier, and pins 1 and 2 are set high.

As a R/L (right/left) turn signal voltage is applied to the turn signal conditioner 160 by the conductor 162, one of the operational amplifiers, U4A or U4B, goes low pulling the F/R (forward/reverse) signal voltage in the conductor 142A down through the resistor R23, the diode CR3, and one of the other diodes, CR4 or CR5.

The resistor R23 and/or the diode CR3 may be omitted, in accordance with design choices.

In operation, the F/R (forward/reverse) signal is pulled down as a function of the R/L turn signal by the turn signal conditioner 160, thereby cooperating with a pair of the null-width generators of FIGURES 9,10, or 11, and optionally cooperating with the rate-of-change controller 144A that is a part of the null-width generators of FIGURES 10 and 11, to prevent fish-tailing of power wheelchairs.

Referring now to FIGURES 13 and 14, the turn signal conditioner 160 of FIGURE 13 includes a comparing circuit 164 and a conditioning circuit 166.

A turn signal conditioner 170 of FIGURE 14 also includes the comparing circuit 164. However, the comparing circuit 164 of FIGURE 14 is illustrated symbolically by a box in phantom lines that contains the operational amplifiers, U4A and U4B, also shown in phantom lines.

Referring now to FIGURE 14, the turn signal conditioner 170, rather than including the conditioning circuit 166 of FIGURE 13, includes a

conditioning circuit 172. The conditioning circuit 172, includes six diodes CR6, CR7, CR8, CR9, CR10, and CR11, three resistors, R25, R26, and R27, and a potentiometer RV4.

If the turn signal conditioner 170 is used with a system in which the null voltage is 2.5 volts, and if the maximum signal voltage, as limited by the signal limiters 48A and 48B of FIGURE 1, is 0.9 volts, then the maximum voltage for a forward signal is 3.4 volts, and the minimum voltage for a reverse signal is 1.6 volts.

The operational amplifiers U4A and U4B are configured to provide 2.8 volts on pins 1 and 2 when there is no R/L turn signal. That is, the R/L turn signal voltage, as applied to the conductor 162, is 2.5 volts.

When the maximum F/R signal voltage is 3.4 volts, with a 0.6 voltage drop across the diodes CR10 and CR11, the voltage applied to the pins 1 and 2 is 2.8 volts, which is the same voltage that the pins 1 and 2 are producing from the operational amplifiers U4A and U4B, so the turn signal conditioner 170 is not conditioning the F/R signal voltage.

However, if the R/L turn signal voltage in the conductor 162 increases for a right turn, since the operational amplifier U4A is an inverting amplifier, the pin 2 will decrease pulling the F/R signal voltage down through the resistor R25, the potentiometer RV4, the resistor R27, and the diode CR10. Conversely, if the R/L signal voltage in the conductor 162 decreases for a left turn, the output of the operational amplifier U4B will decrease, pulling the F/R signal voltage down.

Operation described thus far for the turn signal conditioners, 160 and 170, of FIGURES 13 and 14, are essentially the same. That is they condition forward-speed voltages as a function of R/L turn signals. The turn signal conditioner 170 of FIGURE 14 adds conditioning of the reverse speeds as a function of R/L turn signals.

As mentioned above, a minimum signal voltage of 1.6 volts produces a maximum reverse speed. With the pins 1 and 2 set at 2.8 volts, and with series-connected diodes CR6 and CR7 producing a maximum voltage drop of 1.2 volts, or with series-connected diodes CR8 and CR9 producing a voltage drop of 1.2 volts, the voltage delivered from pins 1 and 2, through the

respective pair of diodes, CR6 and CR7, or CR8 and CR9, to a F/R conductor 174 will be 1. 6 volts.

Thus, when there is no R/L turn signal, that is when the R/L turn signal voltage in the conductor 162 is 2.5 volts, the turn signal conditioner 170 will have no effect on the reverse speed.

However, assuming that the R/L turn signal increases, the noninverting operational amplifier U4B will produce an increased voltage on pin 1, and this increase above the set point of 2.8 volts, although reduced by flowing through the diodes CR8 and CR9, will cause an increase in voltage in the F/R conductor 174, thereby slowing reverse speeds as a function of R/L turn signals.

Referring again to FIGURES 13 and 14, while the use of diodes, as voltage dropping devices, has been taught herein, it should be understood that this is only one of various types of solid-state devices that could be used to provide voltage drops in place of the diodes. For instance, it is well known that other solid state devices, such as transistors and FETS also provide voltage drops.

Referring now to FIGURES 1,15, and 16 the null timer 62 of FIGURE 1 controls the LED indicators 64A, 64B, and 64C by controlling communication to ground, as shown in FIGURES 15 and 16.

As mentioned previously, the amber LED standby indicator 64A shows that the interface 10 has power, the blue LED delay indicator 64B indicates that the delay is in progress, and the green LED active indicator 64C indicates that the interface 10 is active.

X-Y input devices on some power wheelchairs can be used to control auxiliary functions following the nulling of both output signals, so it would be helpful for a user to know when both of the outputs are nulled, and to be able to accomplis this without resorting to an addition LED indicator.

Referring now to FIGURE 15, an X-Y null indicator 180 lights one of the LED indicators, preferably the blue LED indicator 64B, at a lower intensity to indicate that both the null-width indicators, such as the null-width generators, 52A and 52B are producing the null voltage N.

As shown in FIGURE 15, preferably, it is the null indicator that burns at less intensity, although, optionally, full intensity may be used for the null

indicator, and a lessor intensity may be used for one of the three indications previously mentioned.

The X-Y null indicator 180 includes n-channel MOSFETS Q5 and Q6, a resistor R28, and zener diodes CR12 and CR13.

As shown in FIGURE 15, the blue LED indicator 64B is connected to ground through the null timer 62 to produce full intensity. For half-bright intensity, the blue LED indicator 64B is grounded through the resistor R8, the MOSFET Q5, and the MOSFET Q6.

A gate G of the MOSFET Q5 is connected to pins 1 and 2 of the comparators U3A and U3B of either the null-width generator 130A of FIGURE 10 or the null-width generator 150A of FIGURE 11, as indicated by showing the comparators U3A and U3B in phantom lines in FIGURE 15.

A gate G of the MOSFET Q6 is similarly connected to comparators U3C and U3D of a null-width generator, not shown, identical to null-width generators 130A or 150A, thereby providing a null signal for the input device 12B of FIGURE 1.

When both axes, X and Y, are nulled, all four comparators, U3A, U3B, U3C, and U3D produce highs, the pull-up resistors R11 and R29 pull up voltage for respective ones of the gates G, both of the MOSFETS, Q5 and Q6, conduct, and the blue LED indicator, 64B is connected to ground through the MOSFETS, Q5 and Q6, that cooperate to provide AND logic.

Referring now to FIGURE 16, in an X-Y null indicator 190, an AND gate 192 is used to provide AND logic, rather than using the MOSFETS Q5 and Q6 of FIGURE 15. Further, since AND gate 192 separates the comparators, U3A, U3B, U3C, and U3D from the pull-up resistors, R11 and R28 of FIGURE 15, a different pull-up resistor, R29, is used.

Operation is the same as described for FIGURE 15, namely, when all outputs of the comparators, U3A, U3B, U3C, and U3D, are high, the gate G of a n-channel MOSFET Q7 is high, and the MOSFET Q7 conducts, connecting the blue LED indicator 64B to ground through the resistor R28, thereby providing half-bright illumination of the blue LED indicator 64B. The zener diodes CR12, CR13, and CR14 of FIGURES 15 and 16 are provided to protect the gates G from transient voltages.

Referring now to FIGURE 17, a headset 200 includes the tilt-axis X-Y input device 14 of FIGURES 5 and 6 and a chin-actuated switch 202; so that the person 84 may provide the switching function of the switch 60 by moving his chin 204 downward slightly.

While the headset 200 is only one of many headsets that may be used with the present invention, if the headset 200 is used, preferably, the chin- actuated switch 202 is made from material manufactured by Tapeswitch in Farmington, New York.

Referring now to FIGURE 18, a head-actuated, or body-component actuated, mouse, 210, which may be used as a cursor-control system for a computer, or controllable device, 212, or as a head-actuated control for various types of controllable devices, includes the tilt-axis X-Y input device, or first human input device, 14 of FIGURE 1.

The head-actuated mouse 210 also includes the signal conditioner 10 of FIGURE 1, or any combination of the components/functions described herein.

Most importantly, as used in the head-actuated mouse 210 of FIGURE 18, the signal conditioner 10 includes a pair of null compensators, such as the null compensators, 53A and 53B of FIGURES 1 and 8.

Inclusion of a pair of the null compensators, 53A and 53B, frees the user from choosing between two unfortunate choices: attempting to exactly position the headset 200 on the head 83 to achieve a null output voltage, or working with the head 83 cocked at an uncomfortable angle to compensate for initial inexact positioning of the headset 200 on the head 83.

Of perhaps equal importance is inclusion of a pair of null-width generators, such as the null-width generators 52A and 52B of FIGURES 1 and 9, the null-width generator 130A of FIGURE 10, or the null-width generator 150A of FIGURE 11.

Inclusion of a pair of null-width generators, such as the null-width generators 52A and 52B, allows both inclusion of, and adjustment of, a null width to the motor skills of the person 84 in positioning of the head 83. With some paralyzed persons, head movement may be extremely limited, so that a

narrow null width is desirable. With others, body tremors may dictate use of a relatively-large null width.

The head-actuated mouse 210 also includes a second human input device, or mouse-clicking device, 214. Among the many possibilities, the chin- actuated switch 202 of FIGURE 17, a foot switch (not shown), or a certain key on a computer keyboard (not shown) may be used as the second human input device 214.

Optionally, a prioritize select 216 is included for use with computer programs that do not prioritize X or Y movement of a cursor 218 of a computer monitor 220, and for other controllable devices in which optimal operation can be achieved by inclusion of a prioritize function.

For instance, computer assisted drawing (CAD) systems typically prioritize movement along the axis that has the largest input so that perfectly straight lines can be drawn with ease.

If the prioritize select 216 has been set to give priority to X signals, when an X signal enters the prioritize select 216, if an X signal is greater than a Y signal, or occurs before a Y signal occurs, the Y signal is locked out, and the cursor 218 is allowed to move only in left and right X directions, as shown in FIGURE 18.

That is, the prioritize select 216 may be configured to sense the first occurring signal, X or Y, or the greater signal, X or Y. As used herein, a greater signal refers to the absolute value in relation to a null.

A human interface device (HID) 222 is interposed between the prioritize select 216 and the computer 212. The HID 222 translates inclination of the head 83 of the person 84 of FIGURES 5,6, and 15, and the resultant proportional outputs from the tilt sensors, 12A and 12B of FIGURE 1, into computer langage. Preferably, velocities of movement of the cursor 218 of the monitor 220 of the computer 212 are proportional to head inclination angles 87A and 88A of FIGURES 5 and 6.

That is, preferably, instead of requiring a continuous input movement, as do conventional mice, the head-actuated mouse 210 of the present invention, whether head actuated or actuated by any other suitable means,

continues to move the cursor 218, proportional to the angles 87A and 88A of FIGURES 5 and 6, as long as the head 83 is incline.

The HID 222, in addition to translating inputs from the first human input device 14 into computer langage, provides means for making connection to the second human input device 214.

Optionally, a voice-recognition IC 224 is used as the second human input device 214. With inclusion of the voice-recognition IC 224, the head- actuated mouse 210 becomes a head-voice control 226 for the computer 212, and other controllable devices, such as the power wheelchair 80 of FIGURE 4.

The HID 222 may be obtained from Fairchild Semiconductor in South Portland, Maine. One model is shown on data sheet USB 100. The voice- recognition IC 224 may be obtained from Sensory Inc. in Sunnyvale, California.

In operation, movement of the cursor 218 is as described above.

"Pointing"to programs and/or operating functions may be made by head- actuation of the head-actuated mouse 210 and subsequent"clicking"by the chin-actuated switch 202 of FIGURE 17. Optionally,"clicking"may be accomplished by the voice-recognition IC 224; a sound pressure switch that is sensitive to a breathing, whistling, or clicking sound made by the mouth or tongue; a proximity switch; or by any other means.

For use with CAD drawing programs and other complex computer programs, preferably, the voice-recognition IC 224 is used for the second human input device 214. Programs and program functions are selected by voice command into the voice-recognition IC 224, and inclination angles, 87A and 88A of FIGURES 5 and 6, respectively, are used to quantify cursor movements.

While use of the tilt-axis X-Y input devices, 14 and 28, and the joystick X-Y input device, 22, have been described, and while the tilt-axis X-Y input device 14 has been shown and described as being mounted to the head 83 of the person 84, the present invention includes the use of X and Y axis input devices, whether of the joystick type, tilt-axis type, or any other type, mounted to, or actuated by, proximity to, separate body members.

Further, while only X and Y axis operation has been shown and described, the present invention includes Z axis actuation. Z axis input of the

present invention includes actuation of a Z, or third, input device by any body member, whether mounted thereto or not. Preferably Z axis input is achieved by a head-actuated rotational-position sensor in which Z axis input is achieved by the person 84 positionally-rotating the head 83, although an accelerometer may be used as an input device for the Z axis, or any axis.

Finally, while control of the power wheelchair, 80 and the computer, 212 has been shown and described herein, the present invention is applicable to various other types of controllable devices.

Summarizing briefly, the tilt-axis X-Y input device, 14 of FIGURE 17 will not be perfectly positioned on a head 83 of a person 84 during start up, so an initializing signal, or error signal will be produced during a time delay that is provided by the null timer 62.

The null timer 62 provides means for preventing actuation of the controllable device 80, or movement of the cursor 218, by the initializing signal, by holding an output signal in the conductor 72A to a null N.

During the time delay, the initializing signal is stored in the offset storage device 44A. The null compensator 53A, which includes both the offset storage device 44A and an offset buffer 46A, cooperate to provide means for compensating subsequent outputs of the tilt-axis X-Y input device 14.

The use of any pair of the null-width generators 52A, 130A, or 150A, provides means for preventing actuation of the controllable device 80, or movement of the cursor 218 when X and Y output signals are within an adjustable null width.

The rate-of-change controller 144A provides means for progressively obviating the preventing step of the null width generator 52A, 130A, or 150A, subsequent to the output signal moving outside the predetermined null width.

Use of one of the turn-signal conditioners, 160 or 170, provides means for changing an output signal of the Y axis as a function of an output signal of the X axis, thereby slowing speed of the controllable device 80 as a function of the severity of turns.

When increases in the Y output signal produce increases in forward speeds and decreases in the Y output signal produce increases in reverse speeds, the turn-signal conditioner 170 provides means for reducing the Y

output signal as a function of the X output signal for forward propulsion, and increasing the Y output signal as a function of the X output signal for reverse propulsion, thereby providing means for slowing both forward and reverse speeds of the controllable device 80 as a function of the severity of turns.

While the X-Y null indicators, 180 of FIGURE 15 and 190 of FIGURE 16, have been shown and described as providing half-bright illumination of a LED indicators, more basically, these circuits are as they are named. They are indicator circuits that provide an output when both X and Y output signals are nulled.

While input devices have been shown and described that produce output signals in the form of voltages, it should be understood that the present invention can be practiced using input devices that produce other types of signals.

While specific apparatus and method have been disclosed in the preceding description, it should be understood that these specifics have been given for the purpose of disclosing the principles of the present invention, and that many variations thereof will become apparent to those who are versed in the art. Therefore, the scope of the present invention is to be determined by claims included herein without any limitation by numbers that may be parenthetically inserted in the claims.